Disable preinstall images in rootless builds

[dmach]

No description provided.

[pep8speaks]

Hello @dmach! Thanks for opening this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file osc/build.py:

Line 1133:121: E501 line too long (122 > 120 characters)

[codecov]

Codecov Report

Attention: 8 lines in your changes are missing coverage. Please review.

Comparison is base (c790134) 30.75% compared to head (3d20497) 30.75%.
Report is 7 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1444      +/-   ##
==========================================
- Coverage   30.75%   30.75%   -0.01%     
==========================================
  Files          49       49              
  Lines       17742    17744       +2     
==========================================
  Hits         5457     5457              
- Misses      12285    12287       +2     

Files	Coverage Δ
osc/__init__.py	100.00% <100.00%> (ø)
osc/commandline.py	19.08% <0.00%> (ø)
osc/build.py	6.55% <14.28%> (-0.02%)	⬇️

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